A-134974 is a novel and selective adenosine kinase (AK) inhibitor with IC50 = 60 pM. Systemic A-134974 (i.p.) dose dependently reduced hyperalgesia (ED50= 1 μmol/kg) and at higher doses, reduced locomotor activity (ED50 = 16 μmol/kg). Administration of A-134974 intrathecally (i.t.) was more potent (ED50= 6 nmol) at producing antihyperalgesia than delivering the compound by intracerebralventricular (ED50 = 100 nmol, i.c.v.) or intraplantar (ED50 >300 nmol) routes. In contrast, i.c.v. administration of A-134974 was more effective in reducing locomotor activity than i.t. administration (ED50 values were 1 and >100 nmol, respectively). Increasing the pretreatment time for i.t.-delivered A-134974 caused a greater reduction in locomotor activity (ED50= 10 nmol). This was due to diffusion of A-134974 (i.t.) to supraspinal sites. These data demonstrate that the novel AK inhibitor A-134974 potently reduces thermal hyperalgesia primarily through interactions with spinal sites, whereas its ability to depress locomotor activity is predominantly mediated by supraspinal sites.
